The present invention relates generally to security systems that monitor for undesired conditions at a monitored area, and more particularly to an efficient and low cost method and apparatus for notifying at least one security post of an undesired condition at a monitored area with low incidence of false alarms.
Security monitoring systems now commonly use a video camera for monitoring an area. In some cases, the image of the monitored area stays constant with time for a relatively long time period. Thus, some security systems detect for a change in the image of the monitored area with time for detecting movement within the monitored area. For example, U.S. Pat. No. 3,812,287 to Lemelson, U.S. Pat. No. 3,828,125 to Fagan et al., and U.S. Pat. No. 4,777,526 to Saitoh et al. disclose a security system that detects for a change in the image of the monitored area with time for detecting undesired movement within the monitored area.
Unfortunately, with the prior art security system, when an undesired movement within the monitored area is detected, the means for dealing with this detection may not be effective for quickly preventing damage to the monitored area. In order to minimize false alarms, a security guard typically views the image of the monitored area before traveling to the monitored area when an undesired condition has been detected. U.S. Pat. No. 3,812,287 and U.S. Pat. No. 3,828,125 disclose a security system having a monitor that displays an image and that generates an alarm to draw the attention of a security guard to the monitor when an undesired condition has been detected. However, such a system is not effective for monitoring a large number of areas by one security guard. For example, it may be desired to monitor a neighborhood of hundreds of houses. In that case, a monitor for each of the houses would be needed with these prior art security systems which would be costly.
U.S. Pat. No. 4,777,526 discloses a security monitor system which is designed to transmit video signals from a plurality of video information sources via a common transmission line using modulation techniques. Although this security system is amenable for monitoring a large number of areas, additional infrastructure including the modulators, transmitters, and receiving circuitry is needed which adds to the complexity and cost of the system.
Thus, an improved security monitor system wherein one or a few security guards can monitor a large number of areas in a cost effective manner is desired.
Accordingly, the present invention is a security monitor system which effectively monitors a large number of areas in a cost effective manner using already existing communications infrastructure. More specifically, the method and apparatus of the present invention warns at least one security post of an undesired condition at a monitored area by sending a fax via a phone line and/or by sending an E-mail with an attachment of a JPEG color image of the monitored area via a global telecommunications network such as the Internet.
Generally, the present invention includes a camera for creating a first image of the monitored area at a first time point and for creating a second image of the monitored area at a second time point. In addition, a data storage device stores the first image and the second image, and an image processor, coupled to the data storage device, compares the first image with the second image. A fax modem, coupled to the image processor, sends a fax of the second image to the at least one security post if the second image is substantially different from the first image.
The present invention may further include an Internet modem, coupled to the image processor, for sending a JPEG file of the second image as an electronic mail to a predetermined security post if the second image is substantially different from the first image.
The present invention may be used to particular advantage when a dual tone multi-frequency detector detects a remote request via a phone line for a requested fax of the second image and for accepting a fax number entered via the phone line to which the requested fax is to be sent. The image processor then sends a fax of the second image to that accepted fax number.
The image processor within the security system of the present invention repeats comparing another first image to another second image every predetermined time period.
The present invention may be used to particular advantage when the algorithm for comparing the second image to the first image includes determining and comparing the following four parameters of the first image and the second image: an average pixel value, a standard deviation pixel value, an x-coordinate pixel massive center, and a y-coordinate pixel massive center. The first image is substantially different from the second image if the average pixel value of an image block in the first image is substantially different from the average pixel value of the image block in the second image or if the standard deviation pixel value of the image block in the first image is substantially different from the standard deviation pixel value of the image block in the second image or if the x-coordinate pixel massive center of the image block in the first image is substantially different from the x-coordinate pixel massive center of the image block in the second image or if the y-coordinate pixel massive center of the image block in the first image is substantially different from the y-coordinate pixel massive center of the image block in the second image.
In another embodiment of the present invention, the security monitoring system further includes a plurality of cameras with each camera monitoring a respective monitored area. The plurality of cameras are coupled to a computer having an image processor which multiplexes between the plurality of cameras to detect an undesired condition at the respective monitored area of any selected one of the plurality of cameras at a given time.
In this manner, the present invention upon detecting an undesired condition at the monitored area uses already available technology such as fax over the phone lines or electronic mail over the Internet for alerting at least one security post of the undesired condition. As a result, the present invention is a cost effective security system which may monitor a large number of areas. Any area may fax or E-mail an image to a security post such as the police station. The security guard views the faxed and/or electronically mailed image to ensure that a trip to the monitored area is warranted. Thus, false alarms are minimized with the present invention.
These and other features and advantages of the present invention will be better understood by considering the following detailed description of the invention which is presented with the attached drawings.